The brain signature of paracetamol in healthy volunteers: a double-blind randomized trial

Gisèle Pickering,1–3 Adrian Kastler,4 Nicolas Macian,1,2 Bruno Pereira,5 Romain Valabrègue,6 Stéphane Lehericy,6 Louis Boyer,4,7 Claude Dubray,1–3 Betty Jean4 1CHU Clermont-Ferrand, Centre de Pharmacologie Clinique, 2Centre d’Investigation Clinique – Inserm 1405, 3Clermont Université, Laboratoire de Pharmacologie, Faculté de médecine, 4CHU Gabriel Montpied, Clermont-Ferrand, Service d’Imagerie Ostéo-articulaire thoracique et neurologique, 5CHU Clermont-Ferrand, Délégation Recherche Clinique et à l’Innovation, Clermont-Ferrand, France; 6Institut du Cerveau et de la Moelle epiniere – ICM, Centre de NeuroImagerie de Recherche CENIR, Inserm U1127, CNRS UMR 7225, Sorbonne Universités, UPMC University Paris, Paris, France, Department of Neuroradiology, Groupe Hospitalier Pitié-Salpêtrière, Paris, France; 7UMR CNRS UdA 6284, Clemont-Ferrand, France Background: Paracetamol’s (APAP) mechanism of action suggests the implication of supraspinal structures but no neuroimaging study has been performed in humans.Methods and results: This randomized, double-blind, crossover, placebo-controlled trial in 17 healthy volunteers (NCT01562704) aimed to evaluate how APAP modulates pain-evoked functional magnetic resonance imaging signals. We used behavioral measures and functional magnetic resonance imaging to investigate the response to experimental thermal stimuli with APAP or placebo administration. Region-of-interest analysis revealed that activity in response to noxious stimulation diminished with APAP compared to placebo in prefrontal cortices, insula, thalami, anterior cingulate cortex, and periaqueductal gray matter.Conclusion: These findings suggest an inhibitory effect of APAP on spinothalamic tracts leading to a decreased activation of higher structures, and a top-down influence on descending inhibition. Further binding and connectivity studies are needed to evaluate how APAP modulates pain, especially in the context of repeated administration to patients with pain. Keywords: paracetamol, nociception, fMRI, pharmacology, pain&nbsp